A vehicle body side section structure is disclosed, for example, in Patent Literature 1, which includes a roof side rail disposed on an upper part of a lateral side section of a vehicle body and extending in a longitudinal direction of the vehicle body, a roof panel mounted on the roof side rail, a step part formed on the roof side rail to mount a slide rail thereon, and a pillar (center pillar) and a roof arch connected to the roof side rail.
The pillar and the roof arch are connected to the roof side rail in a vicinity of a vertical wall forming a front end section of the step part. According to the vehicle body side section structure, the pillar and the roof arch can be firmly connected to the roof side rail.
In the vehicle body side section structure disclosed in Patent Literature 1, in order to provide a wider opening for a slide door, a front end of a slide rail accommodation recess is positioned forward of a connection section to which the center pillar is joined. With this arrangement, however, since the connection section to which an upper end of the pillar is connected is located on a space of the slide rail accommodation recess, there is concern that a load from the center pillar would not be fully transmitted toward a roof. In other words, the strength and rigidity of the lateral side section of the vehicle body against a side collision would not be ensured.